Pyrimidine nucleoside phosphorylase and dihydropyrimidine dihydrogenase activities as predictive factors for the efficacy of doxifluridine together with mitomycin C as adjuvant chemotherapy in primary colorectal cancer.

BACKGROUND/AIMS: Pyrimidine Nucleoside Phosphorylase (PyNPase) converts 5'-deoxy-5-fluorouridine (5'-DFUR, doxifluridine) to 5-fluorouracil (5-FU). While this reaction is taking place Dihydropyrimidine Dihydrogenase (DPD) catalyzes 5-FU to inactive molecules. Mitomycin C (MMC) elevates the PyNPase level in tumor cells.

METHODOLOGY

We investigated 17 colorectal cancer patients' PyNPase and DPD activities in tumor and normal tissues using an enzyme-linked immunosorbent assay (ELISA) to assess their clinical significance as indicators for selecting colorectal cancer patients for 5'-DFUR together with MMC as adjuvant chemotherapy.

RESULTS

Six of 17 patients developed experienced a recurrence. Tumor DPD activity of the 6 patients who had a recurrence were higher than those of the 11 patients with no recurrence (p = 0.047). On the other hand, there were no significant differences in both the PyNPase and the PyNPase/DPD (P/D) ratio between the group with recurrence and the group without recurrence. For survival analyses, we designed the cut-off value of tumor PyNPase, DPD and P/D ratio as their median value and classified patients into a higher group and a lower group, but there were no significant differences between the groups.

CONCLUSIONS

The DPD activity in the tumor may be a useful indicator for selecting patients likely respond to 5'-DFUR together with MMC as adjuvant chemotherapy. If tumor DPD is high, we had better select a different anticancer drug.